In the racking of pocket pool or billiard balls prior to the initiation of play, the balls are placed in a line across the table, in threes.
The balls will be lined up on the table, from diamond to diamond., placed in the rack with three of the slots. When finished if desired to use all 15 balls, and in some cases less balls, it will appear in a grid view on the pool table.
It also comes in 4 different sizes, for 6, 7, 8, 9 foot pool tables.